The thing with those is that you go up to the 100+ range and it gets BIG....

The second thing is they get SLOW. F/3.4 wide open, F/4 otherwise? Forget any low light situations.

I found a good compact lense with decent "average" range and yet still produces a good photo (as far as I can tell! no complaints at all so far!) is the Sigma 35-70mm F/2.8. Canon also makes a similarly sized lense in the same zoom range, but I went with the faster Sigma.

That Vivitar Series 1 looks VERY nice, especially at f/2.8. Before getting my Sigma I was gunning for a couple of those used on E-bay, but they strayed well outside of my budget range at the time.

They are, however, big lenses. They add a noticable heft and protrusion from the face of the camera. While my Sigma doesn't quite have the reuputation of those Series 1 lenses, it is compact and lightweight. The only thing that could make it better is if it were FDn. Instead it's FD with twist-lock. I can live with that, though.